1. Field of the invention
This invention relates to a hybrid integrated circuit in which terminal electrodes of a chip component are attached to pads formed in conductive wiring layers.
2. Description of the Related Art
Recently, downsizing, low-profiling, and reduction in weight have been increasingly demanded in chip components used in electronic apparatuses such as portable computers or printers. Therefore, a packaged semiconductor integrated circuit by, as a chip component, attaching a semiconductor element to a substrate and molding the substrate by an insulating resin exists.
FIG. 18 is a related-art packaged semiconductor integrated circuit. For a packaged semiconductor integrated circuit, a bare chip 3 of an LSI or the like is attached to a die pad 1 via a brazing material 2, and electrodes (unillustrated) of the bare chip 3 and lead terminals 5 are connected by thin metal wires 6.
And, the surroundings of the die pad 1 and the bare chip 3 are covered by an insulating resin layer 9. In the aforementioned packaged semiconductor integrated circuit, the lead terminals 5 are attached, by a brazing material 4, to a printed wiring 8 printed on a mounting substrate 7.
In this packaged semiconductor integrated circuit, since the lead terminals 5 are exposed to the outside from the insulating resin layer 9, soldering is easy. However, the mounting size of the whole is great, therein exists a difficulty in downsizing, low-profiling, and reduction in weight.
FIG. 19 and FIG. 20 are a plan view and a sectional view of a hybrid integrated circuit as an improvement of the aforementioned packaged semiconductor integrated circuit.
A bare chip 10 of an LSI or the like is attached to a die pad 12 formed on a conductive wiring layer 11. In addition, electrodes 14 provided at both ends of a chip capacitor 13 are directly brazed to pads 15 formed on a conductive wiring layer 11.
Next, an electrode 16 of the bare chip 10 of an LSI or the like the pads 15 are connected by a thin metal wire 17.
As shown in FIG. 20A, although the upper part of the conductive wiring layer 11 is electrically isolated by isolation grooves 18, the lower part of the conductive wiring layer 11 is still connected.
The conductive wiring layer 11 and bare chip 10 and thin metal wires 17 are entirely covered by an insulating resin 24. Thereafter, a continuous part of the lower part of the conductive wiring layer 11 and the insulating resin 24 is cut together as shown by an alternate long and short dashed line, whereby the conductive wiring layer 11 is completely electrically isolated.
As in FIG. 20B, the undersurface of the conductive wiring layer 11 is exposed through the insulating resin 24. On exposed parts of the conductive wiring layer 11, for electrical connection to the outside, external electrodes 19 are formed by providing a brazing material such as a solder. Furthermore, the positions where the external electrodes are provided are covered by a resist 20 for the purpose of protecting the conductive wiring layer.
FIG. 21 is an enlarged view showing a main part of a hybrid integrated circuit. The terminal electrodes 14 of the chip capacitor 13 are fixedly fitted to the pads 15 formed on the conductive wiring layer 11 by a brazing material 21.
External electrodes 14 of the chip capacitor 13 to form a hybrid integrated circuit are attached, by a brazing material 21, to the pads 15 formed on conductive wiring layer 11.
As shown in FIG. 22, external electrodes 19 of a hybrid integrated circuit are heated to be attached to a wiring 23 of a a board 22. When these are heated, the heat is transmitted to the pads 15, whereby a brazing material 21 which attaches the terminal electrodes 14 to the pads 15 is melted, causing a short-circuit between the pads 15.
In addition, it can be considered that the terminal electrodes 14 and pads 15 are attached by a brazing material with a higher melting point than that of the brazing material 21 to form the external electrodes 21.
However, plating applied to the terminal electrodes 14 contains tin. When the aforementioned heat is transmitted to the terminal electrodes 14, the tin contained in the plating is melted and is melted into the brazing material 21, whereby the melting point of the brazing material 21 is lowered. Therefore, even when a high-melting-point brazing material is used as a brazing material 21, the brazing material 21 is melted, causing a short-circuit between the pads 15.
Furthermore, it can be considered that the terminal electrodes 14 and the pads 15 are attached by use of a conductive adhesive. When the terminal electrodes 14 and the pads 15 are attached by a conductive adhesive, if the conductive adhesive is excessive, this flows out to cause a short-circuit between the pads 15 In addition, when the external electrodes 21 are heated to be attached to the wiring 23 of the board 22, adhesive force of the conductive adhesive is deteriorated and adhesion between the terminal electrodes 14 and the pads 15 becomes insufficient.